1. Field of the Invention
The present invention generally relates to electrophotographic printing machines, and more particularly to an electrophotographic printing machine having a fixing device equipped with a carriage which performs printing.
2. Description of the Prior Art
Recently, there has been considerable activity in the development of serial type electrophotographic printing machines equipped with a carriage employing an electrophotographic process in order to achieve reduction in the cost and down-sizing. In such electrophotographic printing machines, an image transfer is performed so that a carriage is moved in the sheet transporting direction and the vertical direction on a transfer device to which a recording sheet is transported, and a transferred image is fixed on the recording sheet by means of a fixing device having rollers arranged in the sheet transporting direction.
In order to achieve further size reduction, electrophotographic printing machines having a carriage equipped with a fixing device have been developed. Such a carriage has a process unit having an electrostatic latent image carrier and a fixing device. Since the fixing device generates a large amount of heat, it is necessary to thermally isolate the electrostatic latent image carrier and the fixing device from each other. For example, the fixing device is cooled by a cooling device. However, the use of such a cooling device prevents down-sizing. Further, a high pressure generated by a roller of the fixing device and applied to the recording sheet is needed to stably perform the fixing process. However, in this case, an oblique motion of the recording sheet or scattering of toner particles will be caused due to high pressure by the roller. In order to reduce these problems, it is necessary to reduce the roller pressure. However, reduction in the roller pressure leads to unstable fixing.